The present invention relates to a method for recovering a titanium compound, a process for preparing a titanium halide, and a process for preparing a catalyst for polymer production. More particularly, the invention relates to a method for recovering a titanium compound from a waste solution containing a titanium alkoxide and the like, wherein the waste solution is generated in the process for preparing a catalyst for polymer production or a catalyst component for polymer production; a process for preparing a titanium halide from the waste solution; and a process for preparing a catalyst for polymer production from the titanium halide prepared by the process.
As catalysts for use in the production of homopolymers of xcex1-olefins and olefin polymers such as ethylene/xcex1-olefin copolymers, those containing a titanium compound supported on an active magnesium halide are heretofore known. Such olefin polymerization catalysts are, for example, catalysts comprising a solid titanium catalyst component containing magnesium, titanium and a halogen as essential ingredients and an organometallic compound catalyst component. The solid titanium catalyst component containing magnesium, titanium and a halogen as essential ingredients is prepared by, for example, a process comprising contacting a liquid magnesium compound with a liquid titanium compound in the presence of an electron donor such as an alcohol to form a solid product and then further contacting the solid product with a liquid titanium compound to form a solid titanium catalyst component.
In the preparation of the solid titanium catalyst component, a waste solution containing an unsupported titanium compound and other titanium compounds newly produced by the reaction in the preparation process is generated after the recovery of the solid titanium catalyst component. In the conventional method, the waste solution is vacuum distilled to recover these titanium compounds. By this method, however, solid matters are precipitated in the distillation mother liquor or on the tray, so that discharge of the residue in distiller sometimes becomes difficult, or because of occurrence of differential pressure in the column, continuation of distillation sometimes becomes difficult. At present, therefore, distillation is terminated without sufficiently recovering the titanium compound, and the residue in distiller is discarded.
The present invention has been made under such circumstances as described above, and it is an object of the invention to provide a method for recovering a titanium compound from a waste solution containing a titanium alkoxide and the like, wherein the waste solution is generated in the process for preparing a catalyst for polymer production or a catalyst component for polymer production, and to provide a process for preparing a titanium halide from the waste solution. It is another object of the invention to provide a process for preparing a catalyst for polymer production from the titanium halide obtained by the above process.
The method for recovering a titanium compound according to the invention comprises bringing a waste solution containing a titanium alkoxide into contact with a halogenating agent to convert the titanium alkoxide to a titanium halide and then distilling the solution containing the titanium halide to recover the titanium halide from the solution.
The method for recovering a titanium compound according to the invention may comprise distilling a waste solution containing a titanium alkoxide and a titanium halide to recover a part of the titanium halide from the waste solution, bringing a residue in distiller given after the distillation into contact with a halogenating agent to convert at least a part of the titanium alkoxide to a titanium halide and then distilling the solution containing the titanium halide to recover the titanium halide from the solution.
The process for preparing a titanium halide according to the invention comprises bringing a waste solution containing a titanium alkoxide into contact with a halogenating agent to convert the titanium alkoxide to a titanium halide.
The process for preparing a titanium halide according to the invention, in another embodiment, comprises distilling a waste solution containing a titanium alkoxide and a titanium halide to recover a part of the titanium halide from the waste solution and bringing a residue in distiller given after the distillation into contact with a halogenating agent to convert the titanium alkoxide to a titanium halide.
The waste solution is, for example, a solution formed when a catalyst for polymer production or a catalyst component for polymer production is prepared, such as a solution formed when an olefin polymerization solid titanium catalyst component containing titanium, magnesium and a halogen as essential ingredients is prepared by the contact of a magnesium compound, a titanium compound and an electron donor.
The process for preparing a catalyst for polymer production according to the invention comprises using the titanium halide obtained by the above process to prepare a catalyst for polymer production such as a catalyst for polyolefin production.